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+---
+name: mongoatlas
+description: Emulated MongoDB Atlas API for local development and testing. Use when the user needs to manage Atlas projects and clusters locally, perform CRUD operations via the Data API, test MongoDB Atlas integrations, or work with the Atlas Admin API without hitting the real Atlas API. Triggers include "MongoDB Atlas", "Atlas Data API", "emulate MongoDB", "Atlas cluster", "atlas admin", or any task requiring a local MongoDB Atlas API.
+allowed-tools: Bash(npx emulate:*), Bash(emulate:*), Bash(curl:*)
+---
+
+# MongoDB Atlas API Emulator
+
+Fully stateful MongoDB Atlas emulation with two API surfaces: the Atlas Admin API for infrastructure management (projects, clusters, database users) and the Data API for document CRUD and aggregation. All state persists in memory.
+
+## Start
+
+```bash
+# MongoDB Atlas only
+npx emulate --service mongoatlas
+
+# Default port (when run alone)
+# http://localhost:4000
+```
+
+Or programmatically:
+
+```typescript
+import { createEmulator } from 'emulate'
+
+const atlas = await createEmulator({ service: 'mongoatlas', port: 4000 })
+// atlas.url === 'http://localhost:4000'
+```
+
+## Auth
+
+Admin API endpoints accept any API key. The Data API accepts any `api-key` header value.
+
+```bash
+# Admin API
+curl http://localhost:4000/api/atlas/v2/groups \
+  -H "Authorization: Bearer test_api_key"
+
+# Data API
+curl -X POST http://localhost:4000/app/data-api/v1/action/find \
+  -H "api-key: test_api_key" \
+  -H "Content-Type: application/json" \
+  -d '{"dataSource": "Cluster0", "database": "mydb", "collection": "users"}'
+```
+
+## Pointing Your App at the Emulator
+
+### Environment Variable
+
+```bash
+MONGODB_ATLAS_API_BASE=http://localhost:4000
+MONGODB_DATA_API_BASE=http://localhost:4000
+```
+
+### Embedded in Next.js (adapter-next)
+
+```typescript
+// next.config.ts
+import { withEmulate } from '@emulators/adapter-next'
+
+export default withEmulate({
+  env: {
+    MONGODB_ATLAS_API_BASE: `http://localhost:${process.env.PORT ?? '3000'}/emulate/mongoatlas`,
+    MONGODB_DATA_API_BASE: `http://localhost:${process.env.PORT ?? '3000'}/emulate/mongoatlas`,
+  },
+})
+```
+
+```typescript
+// app/emulate/[...path]/route.ts
+import { createEmulateHandler } from '@emulators/adapter-next'
+import * as mongoatlas from '@emulators/mongoatlas'
+
+export const { GET, POST, PUT, PATCH, DELETE } = createEmulateHandler({
+  services: {
+    mongoatlas: {
+      emulator: mongoatlas,
+      seed: {
+        clusters: [
+          { name: 'Cluster0', project: 'Project0', instance_size: 'M10', region: 'US_EAST_1' },
+        ],
+        databases: [
+          { cluster: 'Cluster0', name: 'mydb', collections: ['users', 'posts'] },
+        ],
+      },
+    },
+  },
+})
+```
+
+## Seed Config
+
+```yaml
+mongoatlas:
+  projects:
+    - name: Project0
+      org_id: my_org
+  clusters:
+    - name: Cluster0
+      project: Project0
+      provider: AWS
+      instance_size: M10
+      region: US_EAST_1
+      disk_size_gb: 10
+      mongodb_version: "7.0"
+  database_users:
+    - username: admin
+      project: Project0
+      roles:
+        - database_name: admin
+          role_name: atlasAdmin
+  databases:
+    - cluster: Cluster0
+      name: mydb
+      collections:
+        - users
+        - posts
+```
+
+Without seed config, the emulator creates a default Project0 with one M10 cluster.
+
+## API Endpoints
+
+### Admin API - Projects
+
+```bash
+BASE="http://localhost:4000"
+
+# List projects
+curl $BASE/api/atlas/v2/groups
+
+# Get project by ID
+curl $BASE/api/atlas/v2/groups/<groupId>
+
+# Create project
+curl -X POST $BASE/api/atlas/v2/groups \
+  -H "Content-Type: application/json" \
+  -d '{"name": "New Project", "orgId": "my_org"}'
+
+# Delete project
+curl -X DELETE $BASE/api/atlas/v2/groups/<groupId>
+```
+
+### Admin API - Clusters
+
+Cluster states: `IDLE`, `CREATING`, `UPDATING`, `DELETING`, `DELETED`, `REPAIRING`.
+
+```bash
+# List clusters in project
+curl $BASE/api/atlas/v2/groups/<groupId>/clusters
+
+# Get cluster by name
+curl $BASE/api/atlas/v2/groups/<groupId>/clusters/<clusterName>
+
+# Create cluster
+curl -X POST $BASE/api/atlas/v2/groups/<groupId>/clusters \
+  -H "Content-Type: application/json" \
+  -d '{
+    "name": "Analytics",
+    "clusterType": "REPLICASET",
+    "providerSettings": {
+      "providerName": "AWS",
+      "instanceSizeName": "M10",
+      "regionName": "US_EAST_1"
+    }
+  }'
+
+# Update cluster
+curl -X PATCH $BASE/api/atlas/v2/groups/<groupId>/clusters/<clusterName> \
+  -H "Content-Type: application/json" \
+  -d '{"providerSettings": {"instanceSizeName": "M20"}}'
+
+# Delete cluster
+curl -X DELETE $BASE/api/atlas/v2/groups/<groupId>/clusters/<clusterName>
+```
+
+Clusters include connection strings in their response:
+
+```json
+{
+  "connectionStrings": {
+    "standard": "mongodb://localhost:27017",
+    "standardSrv": "mongodb+srv://cluster0.emulate.local"
+  }
+}
+```
+
+### Admin API - Database Users
+
+```bash
+# List database users
+curl $BASE/api/atlas/v2/groups/<groupId>/databaseUsers
+
+# Get database user
+curl $BASE/api/atlas/v2/groups/<groupId>/databaseUsers/admin/<username>
+
+# Create database user
+curl -X POST $BASE/api/atlas/v2/groups/<groupId>/databaseUsers \
+  -H "Content-Type: application/json" \
+  -d '{
+    "databaseName": "admin",
+    "username": "readonly",
+    "roles": [{"databaseName": "mydb", "roleName": "read"}]
+  }'
+
+# Delete database user
+curl -X DELETE $BASE/api/atlas/v2/groups/<groupId>/databaseUsers/admin/<username>
+```
+
+### Admin API - Databases and Collections
+
+```bash
+# List databases in cluster
+curl $BASE/api/atlas/v2/groups/<groupId>/clusters/<clusterName>/databases
+
+# List collections in database
+curl $BASE/api/atlas/v2/groups/<groupId>/clusters/<clusterName>/databases/<databaseName>/collections
+```
+
+### Data API - Document Operations
+
+All Data API operations use `POST` and require `dataSource`, `database`, and `collection` in the request body.
+
+```bash
+BASE="http://localhost:4000"
+HEADERS='-H "Content-Type: application/json" -H "api-key: test_api_key"'
+
+# Find one document
+curl -X POST $BASE/app/data-api/v1/action/findOne \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{"dataSource": "Cluster0", "database": "mydb", "collection": "users", "filter": {"email": "jane@example.com"}}'
+
+# Find documents (supports filter, projection, sort, limit, skip)
+curl -X POST $BASE/app/data-api/v1/action/find \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{
+    "dataSource": "Cluster0",
+    "database": "mydb",
+    "collection": "users",
+    "filter": {"status": "active"},
+    "sort": {"createdAt": -1},
+    "limit": 10,
+    "projection": {"name": 1, "email": 1}
+  }'
+
+# Insert one document
+curl -X POST $BASE/app/data-api/v1/action/insertOne \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{
+    "dataSource": "Cluster0",
+    "database": "mydb",
+    "collection": "users",
+    "document": {"name": "Jane", "email": "jane@example.com", "status": "active"}
+  }'
+
+# Insert many documents
+curl -X POST $BASE/app/data-api/v1/action/insertMany \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{
+    "dataSource": "Cluster0",
+    "database": "mydb",
+    "collection": "users",
+    "documents": [
+      {"name": "Alice", "email": "alice@example.com"},
+      {"name": "Bob", "email": "bob@example.com"}
+    ]
+  }'
+
+# Update one document (supports $set, $unset, $inc, $push, $pull, $addToSet)
+curl -X POST $BASE/app/data-api/v1/action/updateOne \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{
+    "dataSource": "Cluster0",
+    "database": "mydb",
+    "collection": "users",
+    "filter": {"email": "jane@example.com"},
+    "update": {"$set": {"status": "inactive"}, "$inc": {"loginCount": 1}}
+  }'
+
+# Update many documents
+curl -X POST $BASE/app/data-api/v1/action/updateMany \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{
+    "dataSource": "Cluster0",
+    "database": "mydb",
+    "collection": "users",
+    "filter": {"status": "inactive"},
+    "update": {"$set": {"archived": true}}
+  }'
+
+# Delete one document
+curl -X POST $BASE/app/data-api/v1/action/deleteOne \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{
+    "dataSource": "Cluster0",
+    "database": "mydb",
+    "collection": "users",
+    "filter": {"email": "jane@example.com"}
+  }'
+
+# Delete many documents
+curl -X POST $BASE/app/data-api/v1/action/deleteMany \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{
+    "dataSource": "Cluster0",
+    "database": "mydb",
+    "collection": "users",
+    "filter": {"status": "inactive"}
+  }'
+
+# Aggregate (supports $match, $group, $sort, $limit, $skip, $project, $count, $unwind)
+curl -X POST $BASE/app/data-api/v1/action/aggregate \
+  -H "Content-Type: application/json" \
+  -H "api-key: test_api_key" \
+  -d '{
+    "dataSource": "Cluster0",
+    "database": "mydb",
+    "collection": "users",
+    "pipeline": [
+      {"$match": {"status": "active"}},
+      {"$group": {"_id": "$role", "count": {"$sum": 1}}},
+      {"$sort": {"count": -1}}
+    ]
+  }'
+```
+
+Both `updateOne` and `updateMany` support `upsert: true`.
+
+## Common Patterns
+
+### Project + Cluster + CRUD Flow
+
+```typescript
+import { createEmulator } from 'emulate'
+
+const emu = await createEmulator({ service: 'mongoatlas', port: 4000 })
+const BASE = emu.url
+const headers = { 'Content-Type': 'application/json', 'api-key': 'test_api_key' }
+
+// Insert a document
+await fetch(`${BASE}/app/data-api/v1/action/insertOne`, {
+  method: 'POST',
+  headers,
+  body: JSON.stringify({
+    dataSource: 'Cluster0',
+    database: 'mydb',
+    collection: 'users',
+    document: { name: 'Jane', email: 'jane@example.com', tags: ['admin'] },
+  }),
+})
+
+// Query it back
+const res = await fetch(`${BASE}/app/data-api/v1/action/findOne`, {
+  method: 'POST',
+  headers,
+  body: JSON.stringify({
+    dataSource: 'Cluster0',
+    database: 'mydb',
+    collection: 'users',
+    filter: { email: 'jane@example.com' },
+  }),
+})
+const { document } = await res.json()
+// document.name === 'Jane'
+
+// Update with operators
+await fetch(`${BASE}/app/data-api/v1/action/updateOne`, {
+  method: 'POST',
+  headers,
+  body: JSON.stringify({
+    dataSource: 'Cluster0',
+    database: 'mydb',
+    collection: 'users',
+    filter: { email: 'jane@example.com' },
+    update: { '$push': { tags: 'verified' }, '$inc': { loginCount: 1 } },
+  }),
+})
+```